This subproject examines neuroendocrine function during the early and late phases of abstinence in heavy cocaine users. We are also interested in studying the effects of serotonin uptake inhibition on depressive symptoms in this group. An additional interest is in characterizing the pharmacokinetics of serotonin uptake inhibition in cocaine abusers. It should be emphasized that the study concerns neuroendocrine and neurotransmitter mechanisms, and is not a study of treatment efficacy.